A storage apparatus includes a plurality of storage devices that stores therein data and a storage controller that controls the storage devices, and is intended to provide a host computer with a large-capacity data storage space.
There is a demand for a storage apparatus to save a large amount of data at low cost. To satisfy the demand, there is known a technology to record data after performing lossless compression (hereinafter, referred to simply as compression) on the data. By reducing the data size by compressing data and then recording the data in a storage device, more data can be stored in a storage apparatus than data is recorded in the storage device without being compressed. Accordingly, it is possible to reduce the cost for holding data (the bit cost of a storage medium, the power consumption cost of the storage apparatus, etc.).
As another technology to reduce the amount of data to be stored, there is deduplication technology. It is a technology for a storage apparatus, for example, when having detected that multiple pieces of data with the same content exist in the storage apparatus, to retain one of them in a storage device included in the storage apparatus and not to store the other pieces of data in a storage device.
Compression technology and deduplication technology can be used in combination. For example, Patent Document 1 discloses a storage apparatus that performs a deduplication process on duplicate data in pieces of data transferred from a higher-level device, and compresses data that has not been subjected to deduplication.